Physics 11th Chap 9 : Topic 14 - Maryam Publications

Physics Chapter 9 : Topic 14

Beats

1 / 30

Beats are produced when two waves have:

A) Different amplitudes but same frequency

B) Same frequency and same amplitude

C) Different wavelengths and no interference

D) Slightly different frequencies and interfere with each other

2 / 30

The periodic variation in loudness caused by interference of two waves is called:

A) Resonance

B) Diffraction

C) Beats

D) Polarization

3 / 30

The beat frequency produced by two waves of frequencies $\mathbf{f}_{\mathbf{1}}$ and $\mathbf{f}_{\mathbf{2}}$ is:

A) $\left| \mathbf{f}_{\mathbf{1}}\mathbf{-}\mathbf{f}_{\mathbf{2}} \right|$

B) $\mathbf{f}_{\mathbf{1}}\mathbf{\times}\mathbf{f}_{\mathbf{2}}$

C) $\mathbf{f}_{\mathbf{1}}\mathbf{\ /\ }\mathbf{f}_{\mathbf{2}}$

D) $\mathbf{f}_{\mathbf{1}}\mathbf{+}\mathbf{f}_{\mathbf{2}}$

4 / 30

Two tuning forks produce frequencies $\mathbf{256\ Hz}$ and $\mathbf{260\ Hz}$. The beat frequency will be:

A) $\mathbf{4\ Hz}$

B) $\mathbf{0.98\ Hz}$

C) $\mathbf{16\ Hz}$

D) $\mathbf{516\ Hz}$

5 / 30

During beats, the loud sound occurs when the two waves:

A) Interfere constructively

B) Have different speeds

C) Completely cancel each other

D) Have zero amplitude

6 / 30

The soft sound in a beat phenomenon occurs due to:

A) Refraction

B) Constructive interference

C) Destructive interference

D) Reflection

7 / 30

Two sound waves have frequencies $\mathbf{500\ Hz}$ and $\mathbf{504\ Hz}$. The number of beats heard per second is:

A) $\mathbf{1004}$

B) $\mathbf{2}$

C) $\mathbf{500}$

D) $\mathbf{4}$

8 / 30

If two sound waves have exactly the same frequency, the beat frequency will be:

A) Maximum

B) Double the frequency

C) Equal to frequency of sound

D) Zero

9 / 30

The phenomenon of beats demonstrates:

A) Wave polarization only

B) Wave interference

C) Wave absorption

D) Wave reflection only

10 / 30

For audible beats to be clearly detected, the difference between frequencies should generally be:

A) Equal to the speed of sound

B) Zero only

C) Very large

D) Very small

11 / 30

Two waves of frequencies $\mathbf{400\ Hz}$ and $\mathbf{410\ Hz}$ produce:

A) $\mathbf{5}$ beats per second

B) $\mathbf{10}$ beats per second

C) $\mathbf{810}$ beats per second

D) No beats

12 / 30

In the beat phenomenon, the frequency of individual waves remains:

A) Continuously decreasing

B) Zero

C) Constant

D) Continuously increasing

13 / 30

The sound intensity in beats varies because:

A) The resultant amplitude changes periodically.

B) The frequency changes continuously.

C) The wavelength becomes zero.

D) The medium stops vibrating.

14 / 30

Two waves produce maximum loudness when their phase difference is:

A) Random

B) $\mathbf{\pi\ /\ 2}$

C) $\mathbf{\pi}$

D) $\mathbf{0}$ or $\mathbf{2\pi}$

15 / 30

Two waves produce minimum loudness when their phase difference is:

A) $\mathbf{2\pi}$

B) $\mathbf{4\pi}$

C) $\mathbf{\pi}$

D) $\mathbf{0}$

16 / 30

If the frequency difference between two waves increases, the beat frequency:

A) Remains unchanged

B) Decreases

C) Increases

D) Becomes zero

17 / 30

A musician uses beats to tune an instrument because:

A) Beats increase sound frequency

B) Beats measure amplitude

C) Beats indicate the difference between frequencies

D) Beats eliminate sound

18 / 30

A tuning fork of unknown frequency produces $\mathbf{5}$ beats per second with a $\mathbf{300\ Hz}$ tuning fork. Its frequency may be:

A) $\mathbf{305\ Hz}$ only

B) $\mathbf{295\ Hz}$ only

C) $\mathbf{295\ Hz}$ or $\mathbf{305\ Hz}$

D) $\mathbf{300\ Hz}$ exactly

19 / 30

If two waves have frequencies $\mathbf{100\ Hz}$ and $\mathbf{102\ Hz}$, the time interval between successive beats is:

A) $\mathbf{1\ s}$

B) $\mathbf{2\ s}$

C) $\mathbf{0.5\ s}$

D) $\mathbf{102\ s}$

20 / 30

Beats are not usually produced by two independent light sources because:

A) Light sources are generally incoherent.

B) Light cannot interfere.

C) Light has no wavelength.

D) Light has no frequency.

21 / 30

The mathematical expression for resultant amplitude of two interfering waves depends on:

A) Their medium only

B) Their speed only

C) Their colour only

D) Their phase difference

22 / 30

When two waves of slightly different frequencies interfere, the resultant wave has:

A) Zero amplitude

B) Constant amplitude

C) No frequency

D) Periodically changing amplitude

23 / 30

Two sound waves have frequencies $\mathbf{700\ Hz}$ and $\mathbf{710\ Hz}$. The beat period is:

A) $\mathbf{0.01\ s}$

B) $\mathbf{710\ s}$

C) $\mathbf{10\ s}$

D) $\mathbf{0.1\ s}$

24 / 30

In beat formation, the resultant frequency of sound heard is approximately:

A) Zero

B) The difference of frequencies

C) The average frequency of the two waves

D) Twice the frequency difference

25 / 30

If two tuning forks produce 8 beats per second, their frequencies differ by:

A) $\mathbf{4\ Hz}$

B) $\mathbf{0\ Hz}$

C) $\mathbf{8\ Hz}$

D) $\mathbf{16\ Hz}$

26 / 30

Which condition is necessary for producing audible beats?

A) Amplitudes must be zero.

B) Frequencies must be slightly different.

C) Frequencies must be exactly equal.

D) Frequencies must be extremely different.

27 / 30

At maximum intensity during beats, the resultant amplitude is:

A) Constant

B) Zero

C) Maximum

D) Minimum

28 / 30

At minimum intensity during beats, the resultant amplitude is:

A) Doubled

B) Minimum

C) Maximum

D) Infinite

29 / 30

If two sound sources have frequencies differing by $\mathbf{20\ Hz\ }$, the number of beats heard per second is:

A) $\mathbf{0}$

B) $\mathbf{40}$

C) $\mathbf{10}$

D) $\mathbf{20}$

30 / 30

The beat phenomenon is an application of:

A) Conservation of momentum

B) Photoelectric effect

C) Principle of superposition

D) Coulomb’s law

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